This invention relates to a method of restoring catalytic activity to a spent hydroprocessing catalyst, the resulting hydroprocessing catalyst and its use in a hydroprocessing process.
International publication number WO 01/02092 discloses a process for regenerating a used additive-based catalyst. The regeneration step is carried out by contacting the used additive-based catalyst with oxygen at a temperature of no more than 500° C. The resulting regenerated catalyst more preferably has below 1 wt. % carbon content before it is subjected to a rejuvenation step by being contacted with an organic additive. The method of the publication is limited to additive-based catalysts, and the publication does not recognize a need to control the concentration of carbon on the regenerated catalyst to within a specific range in order to obtain a better benefit from its rejuvenation. In fact, this publication suggests that it is best for the carbon content of the regenerated catalyst to be as low as possible before it is undergoes the rejuvenation treatment. This publication does not disclose that its catalyst rejuvenation step requires the organic additive to remain on the catalyst for an aging period prior to drying.
European patent application publication EP 0 541 994 A1 discloses a process for regenerating a hydrogenation catalyst, comprising a support, a Group VI metal and a Group VIII metal, and having coke deposited thereon, by controlling the oxidative burning of the coke so as not to reduce the residual coke content to less than 0.5 weight percent and to control it within the range of from 0.5 to 10.0 weight percent. This publication notes that too severe oxidation conditions can negatively change the pore structure, surface area, and active sites of the catalyst. The publication does not provide experimental data that compares the activity of regenerated catalyst with the activity of the fresh catalyst, but it only presents comparative data for certain physical properties of the two catalysts. Also, nothing is disclosed concerning revitalization of a spent catalyst using chelating agents and the relationship between carbon removal and a chelation treatment.
U.S. Pat. No. 6,239,066 B1 discloses a process for improving the activity of a catalyst by treatment thereof with a chelating agent. It is noted that the treatment method can also be used to improve the activity of a spent catalyst. Exemplary data presented in an example show that a used catalyst that has been both regenerated and then treated with ethylene diamine tetra acetic acid (EDTA) has better improved relative volumetric activity (RVA) than the used catalyst that has only been regenerated. There is no mention of carbon levels that are on the used catalyst, or the regenerated catalyst, or the regenerated and treated catalyst.
There is an ongoing need to find better methods for restoring the activity of catalysts that have lost activity due to their use, particularly, when the catalyst is a spent high activity hydrotreating catalyst.